When a frame pointer is in use, we can optimize popping all
queued parameters via a simple move from the frame pointer
instead of an addition to the stack pointer.
The new sequence is 4 insns, the old sequence was 9 insns.
Committed.
r~
PR target/34888
* config/avr/avr.md: New splitter for REG_ARGS_SIZE 0.
diff --git a/gcc/config/avr/avr.md b/gcc/config/avr/avr.md
index b8560df..b5aa73c 100644
--- a/gcc/config/avr/avr.md
+++ b/gcc/config/avr/avr.md
@@ -235,6 +235,17 @@
DONE;
})
+;; Notice a special-case when adding N to SP where N results in a
+;; zero REG_ARGS_SIZE. This is equivalent to a move from FP.
+(define_split
+ [(set (reg:HI REG_SP) (match_operand:HI 0 "register_operand" ""))]
+ "reload_completed
+ && frame_pointer_needed
+ && !cfun->calls_alloca
+ && find_reg_note (insn, REG_ARGS_SIZE, const0_rtx)"
+ [(set (reg:HI REG_SP) (reg:HI REG_Y))]
+ "")
+
;;========================================================================
;; move byte
;; The last alternative (any immediate constant to any register) is
